This application is based on application No. 11-74996 filed in Japan, the contents of which is incorporated herein by reference.
1. Technical Field of the Invention
The present invention relates to an apparatus for recording and reproducing data to or from an optical disc, or more specifically, to apparatus discriminating a read only optical disc from a recordable optical disc to perform a suitable reproducing processing dependent on a type of the optical disc.
2. Related Art
In recent years, there have widely been provided a minidisc (MD) recorder, an MD player and the like which can record and reproduce information data by using, as an optical disc, for example a minidisc to be one of writable optical magneto discs.
The MD recorder and the MD player are optical disc recording and reproducing apparatuses which can reproduce both a read only optical disc and a recordable optical disc in the same manner as a compact disc (CD) player and the like.
A first conventional example of such an apparatus, the apparatus is generally known, which discriminates whether an optical disc is a read only optical disc or a recordable optical disc by a sensor hole provided on a cartridge of the optical disc, and switches automatically an operation corresponding to the type of the optical disc for reproducing data.
As a second conventional example of the optical disc recording and reproducing apparatus, an optical disc recording and reproducing apparatus has been disclosed in Japanese Patent Laid-Open Publication No. 3-181062. The apparatus notices a difference in a reflectance on each recording plane of a read only optical disc and a recordable optical disc. The apparatus discriminates whether the optical disc is the read only optical disc or the recordable optical disc based on a difference in a peak level of a reproducing RF signal which is a detection output from the optical pickup. The optical pickup is obtained when an objective lens of an optical pickup is forcibly moved in the direction of an optic axis, that is, when the forcible movement is specifically carried out from a predetermined position beyond a focalized position. Then, the apparatus switches automatically operating conditions depending on the type of the optical disc.
However, each of the optical disc recording and reproducing apparatuses according to the first and second conventional examples has the following problems.
More specifically, in order to automatically switch the operating conditions corresponding to the type of the optical disc and to perform reproducing, it always needs to discriminate independently whether the optical disc is a read only optical disc or a recordable optical disc. In order to attach the optical disc and then reproduce the optical disc, it is required that the operation for discriminating the type of the optical disc should be separated from the operation for switching the operating conditions of the apparatus based on the result of the discrimination and the operations should be interlocked. Thus, timing management is required for each operation.
In the optical disc recording and reproducing apparatus according to the first conventional example, moreover, a detector is required for discriminating the type of the optical disc by using the sensor hole provided on the cartridge holding the optical disc. It causes an increase of the number of components and a cost. In addition, in the case of an optical disc recording and reproducing apparatus of a portable type, it is necessary to provide a space for the detector for discriminating the type of the optical disc, which obstructs a reduction in the size of the apparatus.
In the optical disc recording and reproducing apparatus according to the second conventional example, furthermore, the objective lens of the optical pickup should be passed through the focalized position once in order to discriminate the type of the optical disc. In reproducing operation, for both the read only optical disc and the recordable optical disc, it is necessary to forcibly move the objective lens of the optical pickup toward the focalized position again, and perform the focus servo. Consequently, it takes a long time from the operation for specifying the reproducing operation by a user to the start of the reproducing operation of the is optical disc.
The present invention solves the above-mentioned conventional problems. It provides an optical disc recording and reproducing apparatus which can rapidly and reliably discriminate the status of attachment of an optical disc in an optional position on a disc without requiring a detector other than an optical pickup such as a detector for performing discrimination using a sensor hole provided on a cartridge of the optical disc. The apparatus, without a complicated structure, can also apply a focus servo on optimum operating conditions according to the type of read only and recordable optical discs to perform a reproducing operation simultaneously with the discrimination processing. The apparatus can also shorten a time required from the reproducing operation by a user to the start of the reproducing operation.
In order to solve the above-mentioned problems, the optical disc recording and reproducing apparatus according to the present invention is characterized in that the level of a focus error signal and a peak occurred before focus is obtained are detected while an objective lens is forcibly moved from a predetermined position toward the focalized position (where the focus is obtained), presence of the optical disc and a type of the optical disc (read only type/recordable type) are discriminated based on a certain level, and a focus servo is switched to start a reproducing processing before the objective lens which is being moved toward the focalized position reaches a focalized position when the result of the discrimination indicative of load of the optical disc is obtained.
According to the apparatus with the above described structure, it is possible to rapidly and reliably discriminate the status of load of an optical disc at any position on a disc without requiring a detector other than an optical pickup such as a detector for performing discrimination using a sensor hole provided on a cartridge of the optical disc and without making a structure complicated. It is also to apply a focus servo on optimum operating conditions according to the type of optical discs to perform a reproducing operation simultaneously with the discrimination processing, and to shorten a time required from the reproducing operation by a user to the start of the reproducing operation.
In a first aspect of the present invention, an optical disc recording and reproducing apparatus is provided for recording and reproducing data to an optical disc. The apparatus drives an objective lens in a direction of an optic axis, irradiates a light beam on the optical disc through the objective lens, actuates a focus servo to the objective lens in response to a focus error signal generated based on reflected light from a recording plane of the optical disc, thereby reproducing data recorded on the optical disc.
The apparatus comprises a gain setting section for setting a gain for the focus error signal, and a disc discriminating section for discriminating whether a type of the optical disc which is loaded in the apparatus is a recordable type or a read only type, and discriminating whether the optical disc is loaded in the apparatus.
The gain setting section sets the gain for the focus error signal to a first gain which is specified to a recordable type optical disc before the loaded optical disc is discriminated to be of either of a read only type or a recordable type by the disc discriminating section, and switches the gain of the focus error signal to a second gain which is specified to an read only type optical disc when the optical disc is discriminated to be of the read only type by the disc discriminating section.
While the objective lens is moving toward a focalized position, the disc discriminating section detects a level of the focus error signal and a peak of the focus error signal occurred before focus is obtained, and compares the detected level with a first reference level and a second reference level to discriminate that the optical disc is of the recordable type when the focus error signal exceeds the first reference level and reaches the peak without exceeding the second reference level, and that the optical disc is of the read only type when the focus error signal exceeds the second reference level.
When the disc discriminating section discriminates that the optical disc is loaded, the focus servo is actuated so as to focus a light spot on the recording plane of the optical disc based on the focus error signal before the objective lens moving toward the focalized position reaches a focalized position.
In a second aspect of the invention, an apparatus for recording and reproducing data for an optical disc comprises an optical pickup, a focus driver, a focus error signal generator, a focus servo section, an objective lens moving section, a disc discrimination section, and a gain setting section.
The optical pickup irradiates light beam on an optical disc through a built-in objective lens and detecting reflection light from a recording plane of the optical disc to reproduce information recorded on the optical disc.
The focus driver drives the objective lens of the optical pickup in a direction of an optic axis.
The focus error signal generator generates a focus error signal from an output of the optical pickup.
The focus servo section controls the focus driver such that the light spot is focused on the recording plane of the optical disc in response to the focus error signal.
The objective lens moving section controls the focus driver to forcibly move the objective lens.
The disc discrimination section discriminates presence of the optical disc loaded in the apparatus and discriminating whether the loaded optical disc to be of a recordable type or a read only type based on a level of the focus error signal and predetermined levels, and switches control to the focus driver between control by the objective lens moving section and control by the focus servo section.
The gain setting section sets a gain for the focus error signal to a first gain which is specified for a recordable type optical disc before the optical disc is discriminated to be of either of the read only type or the recordable optical type, and switches the gain for the focus error signal to a second gain which is specified to the read only optical disc when the optical disc is discriminated to be of the read only type, by the disc discriminating section.
The disc discriminating section has functions of detecting the level of the focus error signal and a peak of the focus error signal occurred before the focus is obtained, while the objective lens is moved from a first predetermined position toward the focalized position by the objective lens moving section, discriminating the loaded optical disc to be of the recordable type, when the level of the focus error signal exceeds a first reference level and reaches the peak level without exceeding a second reference level, discriminating the loaded optical disc to be of the read only type, when the level of the focus error signal exceeds the first reference level and exceeds the second reference level before reaching the peak, and discriminating no optical disc to be loaded, when the level of the focus error signal is smaller than the first reference level while the objective lens of the optical pickup is forcibly moved to a second predetermined position beyond the focalized position by the focus driver.
When the loaded optical disc is discriminated to be of either of the read only type or the recordable type, the control to the focus driver is switched to the control by the focus servo section before the focalized position is reached, and when no optical disc is discriminated to be loaded, the objective lens of the optical pickup is forcibly moved to a third predetermined position to stop.
According to above structures, the level of the focus error signal and the peak occurred before focus is obtained are detected while the objective lens is forcibly moved from the predetermined position in the focusing direction, the presence of the optical disc and the type of the disc (read only type/recordable type) are discriminated based on a certain level. When the result of the discrimination that the optical disc is loaded is obtained, the focus servo is switched to start the reproducing processing before the objective lens which is being moved in the focusing direction reaches the focalized position.